Today I had some problems to do a check wether a Rich Text Editor field is filled in or not. I found out that sharepoint also translates the Title of the Rich Text Editor field. That was really unexpected because the iframe is dynamically constructed in the browser. So you would expect that changing the MUI language would translate the Title propertie of the RTE field. So for Frensh, Dutch and English MUI languages you could do the check like below.
Bugfix available at this new blogpost : http://andydevelopments.blogspot.com/2012/10/check-if-sharepoint-richt-text-editor.html